128

INTRODUCTIONTemporal and spatial differences in the frequency of fireeffect ecosystem structure and function. In many fire regimesnon-human ignitions are overwhelmed by anthropogenicignitions. Consequently, human population density, culture,and topography control ignition in these fire regimes affectthe long-term disturbance frequency and species composi-tion. These factors can be quantitatively used to predict thefrequency of fire in ecosystems. The interactions of fuels,ignitions, and topography as they affect the fire regime overa period of 300 years can be derived from analyses of firehistory data.

The scale, frequency, and legacy of disturbance regimesand their effects on the distribution of forest species alsohave important management, policy, and political implica-tions. Debates about even-aged versus uneven-aged man-agement, or no timber harvesting often hinge on what isnatural, or what was the pre-European disturbance regime.Managers and policy makers are often interested in mimick-ing natural disturbance regimes with silvicultural prescrip-tions to foster native plant and animal species diversity(Loucks 1970). The species composition of Ozark forestecosystems is a legacy of their long-term disturbanceregimes. Thus, fire regimes and fire frequencies are associ-ated with the abundance of many species of reptiles, birds,fungi, and plants in the Ozarks. Knowledge of these regimesand their effects is valuable for understanding present-dayforest species composition and structure. We show thelong-term affects of anthropogenic disturbance and topo-graphic roughness on forests, flora, and fauna using datafrom the Missouri Ozark Forest Ecosystem Project (MOFEP),a long-term study initiated to quantify forest managementeffects on flora and fauna (Brookshire and others 1997;Brookshire and Hauser, 1993). The goal of this paper is toillustrate how anthropogenic disturbance and topographyhave been major factors affecting disturbance frequency atthe MOFEP sites and that historic disturbance regimeshave a legacy that continues to affect contemporary plantand animal distributions today.

FIRE HISTORY SUMMARYThe three important factors that determine fire regimes inoak-dominated ecosystems are topographic roughness,human population density, and culture. Specifically, theroughness of the topography around a site mitigates thepropagation of disturbance related factors, such as fire,logging, and human travel into a site. Topographic rough-ness is positively correlated with the length of mean fireintervals. Consequently, fires are less frequent in roughthan in flat terrain, especially during periods of limitedanthropogenic ignitions (fig. 1). The strength and directionof the topographic effect diminishes as the spatial andtemporal frequency of anthropogenic ignitions increases toa point of pyro-saturation (ignitions occur throughout thelandscape and fuels are burned as soon as they are able tosupport the spread of a fire). Since topography generallychanges through time very slowly, its influence on fireregimes is not only long-term but dates to long before thefirst effects of human ignitions.

Fire has been an integral tool in the lives of humans formany thousands of years. Thus, humans are a potentialand dynamic source of ignition, when and wherever theyare present and irrespective of whether landscape burningis promoted (Pyne 1982, 1995) or suppressed (Westin 1992).The early records of fire history support the idea that firefrequency is a function of potential human ignitions. Firefrequency has been correlated with human population in anumber of studies (Dey and Guyette 2000, Guyette andDey 1997, Guyette and others 2002). The positive relation-ship between population density and fire frequency dimin-ishes as ignitions become more frequent and fuels fail toaccumulate. As population density increases further, firefrequency lessens due to change in land use and firesuppression.

Cultural values have influenced wildland fire use andsuppression in different ways through time. Historically firewas used to improve travel, for hunting wild game, to

THE EFFECTS OF HUMANS AND TOPOGRAPHY ON WILDLAND FIRE,FORESTS, AND SPECIES ABUNDANCE

Richard P. Guyette and Daniel C. Dey1

1 Research Associate Professor and Research Forester, The School of Natural Resources, University of Missouri, Columbia, MO 65211,respectively.

Citation for proceedings: Spetich, Martin A., ed. 2004. Upland oak ecology symposium: history, current conditions, and sustainability.Gen. Tech. Rep. SRS–73. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 311 p.

Abstract—Ignitions, fuels, topography, and climate interact through time to create temporal and spatial differences in thefrequency of fire, which, in turn, affects ecosystem structure and function. In many ecosystems non-human ignitions areoverwhelmed by anthropogenic ignitions. Human population density, culture, and topographic factors are quantitativelyrelated to fire regimes and the long-term pattern in fire frequency and species composition. These factors can bequantitatively related and used to reconstruct and predict the frequency of fire in ecosystems and to identify changingfactors involved in anthropogenic fire regimes. Quantitative fire histories from oak-pine sites in Arkansas, Indiana,Missouri, and Ontario are used to examine patterns of interaction in fuels, ignitions, and topography over a period of 300years. Fire regimes and fire frequencies are associated with the abundance of many species of reptiles, birds, fungi, andplants. Human population density and topographic roughness are master variables in understanding temporal and spatialdifferences in fire regimes and their effects on ecosystems.

129

promote nut and berry production, to prepare sites for agri-culture, to improve browsing and grazing conditions, etc.But as a timber economy developed, and people built homesin the hinterlands, suppressing fire became a necessity. Inthe modern era, cultural values have become the mostimportant factors controlling fire frequency as increasingpopulation density increases the risk of wild fire to humansafety and economics. Good pasture may require burningwhile defect free timber may require fire suppression. Unlikeincidental anthropogenic ignitions (proxy: human populationdensity), which stem directly from basic human requirementsfor cooking, transport, warmth and safety, value orientedcultural constraints on wildland fire originate from our socie-ties economic system. This includes fire suppression forperceived and real safety as well as prescribed fire forecosystem diversity, safety, and silvicultural purposes. Theartifact of fire suppression (the human separation of ignitionand fuels) creates its own dangers especially since fuel andeconomic conditions can be highly variable through time.

LONG-TERM LEGACY OF FIRE, DISTURBANCE,AND SPECIES GROUPSLandscape level fire histories and species population dataallow for the study of species abundance, distribution, andbeta diversity within a region. Species groups are sensitiveto the long-term effects of fire and forest disturbance asshown by the data collected on a wide array of species as

part of the Missouri Ozarks Forest Ecosystem Project(Brookshire and Shifley 1997). Data on plant and animalabundances (Kabrick and others 1997, Bruhn and others1997, Clawson and others 1997, Grabner and others 1997,Renkin 1997, Fantz and Renken 1997) at nine sites in theOzarks are associated with regional differences in the his-toric fire and disturbance regimes as quantified by an indexof disturbance (Guyette and Kabrick, 2002). Disturbanceinterval indices are correlated with the abundance of treespecies, small mammals, reptiles, amphibians, birds, herba-ceous plants, fungi, oak species in the overstory, and groundflora (fig. 2). Trees, reptiles, birds, herbaceous plants, andArmillaria species, as groups, all show sensitivity to long-term disturbance regimes. This may be a positive or nega-tive association with fire and disturbance. Amphibians showa lower sensitivity to disturbance. The low sensitivity ofamphibians to disturbance may be explained by their sub-terranean habitat (e.g., salamanders), which may bufferthem from aboveground disturbances and by the limitingeffects on populations of scarce breeding habitat (waterbodies) in the MOFEP study area.

Fire and disturbance result in changes in the distribution oflight and spatial structure of forests that, in turn, regulatesmicroclimate (i.e., light, temperature, humidity and mois-ture). Species have adapted to niches created by varyingfrequencies of disturbance. In the southeastern Ozarks,

Figure 1—Landscape roughness and human population are major factors in disturbanceregimes. Here, mean fire intervals are mapped for the period 1700-1780 in the MOFEP studyregion. Fire intervals are based on the model: MFI = -442.1 + (449.9 x topo) -(0.001 x pop),where MFI is the mean fire interval, topo is an Index of topographic roughness, pop is thenatural log of human population density times the square of river mile (Guyette and Dey 2000).Numbers are site designations and locations for the nine MOFEP sites.

130

several closely related species (fig. 2) are associated withvery different frequencies of disturbance in the same region.The abundances of some closely related (in the same genus)trees, birds, and fungi (Armillaria spp.) have contrastingcorrelations with the frequency of disturbance (table 1).

Figure 2—The association between fire and disturbance and the abundance of 75 species by group. Species near a correlationof 1 on the y-axis are strongly and negatively associated with frequent disturbances. Species near a correlation of -1 on the y-axis are strongly and positively associated with the frequent disturbances. Species near a correlation of 0 on the y-axis are notstrongly associated with the frequency of disturbance. Significant (p < 0.05) correlations for a single species-disturbance test aregreater than 0.60 or less than -0.60. While the power of an individual species test is low (only 9 sites), differences in thesensitivity of species groups to disturbance are evident.

Post oak (Quercus stellata), summer tanagers (Pirangarubra), and Armillaria mellea are found at sites with frequentdisturbance while white oak (Quercus alba), scarlet tanagers(Piranga olivacea), and Armillaria gallica are found inforests with less frequent canopy disturbance.

MOFEP data: Kabrick and others 1997, Fantz andRenken 1997, Renken 1997, Clawson and others1997, Grabner and others 1997, and Bruhn and others,Guyette and Kabrick 2002.

Table 1—Correlation coefficients among genus pairs anddisturbance illustrate how closely related species at the MissouriOzark Forest Ecosystem Project sites are often very different intheir association with long-term disturbance frequencya

Genus LS species, r ES species, r Differenceb, r

Quercus alba, +0.92 stellata, -0.96 alba-stellata, +0.97Armillaria gallica, +0.88 mellea, -0.49 gallica-mellea, +0.84Piranga olivacea, +0.68 rubra, -0.55 olivacea-rubra, +0.79

a Correlation coefficients are for the disturbance interval index (Guyette andKabrick 2002) and species abundances at the nine sites. Note the oppositesigns of correlation coefficients by different species within the same genus.b Difference is the abundances of early successional (ES) species subtractedfrom late successional (LS) species. Significant (P < 0.05) correlations areshown in bold.Source: Bruhn and others (1997); Clawson and others (1997); Guyette andothers, in press; Kabrick and others (1997).

131

ACKNOWLEDGMENTSThe authors thank the Missouri Department of Conservation,the Missouri Ozark Forest Ecosystem Project, the NationalPark Service, and the USDA Forest Service for theirsupport of this research. In addition, the authors thankJ. Bruhn, R. Clawson, J. Grabner, J. Kabrick, R. Renkin,J. Faaborg, D. Fantz, and D. Hamilton for the collection ofMOFEP data. Also, we want to thank Mike Stambaugh forproducing the map of fire intervals.

LITERATURE CITEDBatek, M.J.; Rebertus, A.J.; Schroeder, W.A. [and others]. 1999.

Reconstruction of early nineteenth-century vegetation and fireregimes in the Missouri Ozarks. J. of Biogeography, 26: 397-412.

Brookshire, B.L.; Hauser, C.H. 1993. The Missouri Ozark Forest eco-system project: the effects of forest management on the forestecosystem. In: Gillespie, A.R.; Parker, G.R.; Pope, P.E.; Rink,G.R. eds. Proceedings of the 9th central hardwood forest confer-ence. Gen. Tech. Rep. NC-161. St. Paul, MN: U.S. Departmentof Agriculture, Forest Service, North Central Forest Experiment.

Brookshire, B.L.; Shifley, S.R., eds. 1997. Proceedings of theMissouri Ozark Forest ecosystem project symposium: anexperimental approach to landscape research. Gen. Tech. Rep.NC-193. St. Paul, MN: U.S. Department of Agriculture, ForestService, North Central Forest Experiment Station: 150-168.

Bruhn, J.N.; Wetteroff, J.J., Jr.; Mihail, J.D.; Burks, S. 1997.Determination of the ecological and geographic distributions ofArmillaria species in Missouri forest ecosystems. In: Brookshire,B.L.; Shifley, S.R. eds. Proceedings of the Missouri OzarkForest Ecosystem Project symposium: An experimentalapproach to landscape research. Gen. Tech. Rep. NC-193. St.Paul, MN: U.S. Department of Agriculture,

Clawson, R.L.; Faaborg, J.; Seon, E. 1997. Effects of selectedtimber management practices on forest birds in Missouri oak-hickory forests. In: Brookshire, B.L.; Shifley, S.R. eds.Proceedings of the Missouri Ozark Forest Ecosystem Projectsymposium: An experimental approach to landscape research.Gen. Tech. Rep. NC-193. St. Paul, MN: U.S. Department ofAgriculture, Forest Service, North Central Forest ExperimentStation: 274-288.

Cutter, B.E.; Guyette, R.P. 1994. Fire history of an oak-hickoryridge top in the Missouri Ozarks. American Midlands Naturalist.132: 393-398.

Fantz, D.K.; Hamilton, D.A. 1997. Abundance and production ofberry-producing plants on the MOFEP study sites: the soft maststudy pre-harvest conditions (1994-1995). In: Brookshire, B.L.;Shifley, S.R. eds. Proceedings of the Missouri Ozark ForestEcosystem Project symposium: An experimental approach tolandscape research. Gen. Tech. Rep. NC-193. St. Paul, MN:U.S. Department of Agriculture, Forest Service, North CentralForest Experiment Station: 210-230.

Grabner, J.K.; Larsen, D.R.; Kabrick, J.M. 1997. An analysis ofMOFEP ground flora: pre-treatment conditions. In: Brookshire,B.L.; Shifley, S.R. eds. Proceedings of the Missouri OzarkForest Ecosystem Project symposium: An experimentalapproach to landscape research. Gen. Tech. Rep. NC-193. St.Paul, MN: U.S. Department of Agriculture, Forest Service,North Central Forest Experiment Station: 169-197.

Guyette, R.P.; Cutter, B.E. 1997. Fire history, population, andcalcium cycling in the Current River watershed. In: Pallardy,S.G.; Cecich, R.A.; Garrett, H.G.; Johnson, P.S. eds.Proceedings 11th Central Hardwood Forest Conference. Gen.Tech. Rep. NC-188. St. Paul, MN: U.S. Department ofAgriculture, Forest Service, North Central Forest ExperimentStation: p. 354-372.

Guyette, R.P.; Dey, D.C. 2000. Humans, topography, and wildlandfire: the ingredients for long-term patterns in ecosystems. In:Proceeding: Workshop on fire, people, and the CentralHardwood Landscape, D.A. Yaussey, compiler.

Guyette, R.P.; Kabrick, J.M. 2002. The legacy and continuity offorest disturbance, succession, and species at the MOFEPsites. In: Proceedings of the second Missouri Ozark ForestEcosystem Project symposium (Shifley and Kabrick eds.).USDA Forest Service. GTR NC-227, 227 p.

Guyette, R.P.; Muzika, R.M.; Dey, D.C. 2002. Dynamics of ananthropogenic fire regime. Ecosystems 5: 472-486.

Guyette, Richard P.; Muzika, Rose-Marie; Kabrick, John;Stambaugh, Michael C. [In press]. A perspective on Quercuslife history characteristics and forest disturbance. In: Spetich,M.A., ed. Upland oak ecology symposium: history, currentconditions, and sustainability. Gen. Tech. Rep. Asheville, NC:U.S. Department of Agriculture, Forest Service, SouthernResearch Station.

Kabrick, J.M.; Larsen, D.R.; Shifley, S.R 1997. Analysis of pre-treatment woody vegetation and environmental data for theMissouri Ozark Forest ecosystem project. In: Brookshire, B.L.;Shifley, S.R. eds. Proceedings of the Missouri Ozark ForestEcosystem Project symposium: An experimental approach tolandscape research. Gen. Tech. Rep. NC-193. St. Paul, MN:U.S. Department of Agriculture, Forest Service, North CentralForest Experiment Station: 150-168.

Loucks, O. 1970. Evolution of diversity, efficiency and communitystability. Am. Zool., 10: 17-25.

Meinert, D.; Nigh, T.; Kabrick, J. 1997. Landforms, geology, andsoils of the MOFEP study area. In: Brookshire, B.L.; Shifley,S.R. eds. Proceedings of the Missouri Ozark Forest EcosystemProject symposium: An experimental approach to landscaperesearch. Gen. Tech. Rep. NC-193. St. Paul, MN: U.S.Department of Agriculture, Forest Service, North Central ForestExperiment Station: 56-68.

Nigh, T.; Buck, C.; Grabner, J. [and others]. 2000. An ecologicalclassification system for the Current River Hills subsection.Missouri Department of Conservation. Jefferson City, Missouri.30 p.

Pyne, S.J. 1982. Fire in America: a cultural history of wildland andrural fire. Princeton, NJ: Princeton University Press. 654 p.

Pyne, S.J. 1995. World fire: the culture of fire on Earth. New York:Henry Holt and Co. 379 p.

Renken, R.B. 1997. Pre-treatment conditions of herpetofaunalcommunities on Missouri Ozark Forest ecosystem project(MOFEP) sites, 1992-1995. In: Brookshire, B.L.; Shifley, S.R.eds. Proceedings of the Missouri Ozark Forest EcosystemProject symposium: An experimental approach to landscaperesearch. Gen. Tech. Rep. NC-193. St. Paul, MN: U.S.Department of Agriculture, Forest Service, North CentralForest.

Schurbon, J.M. 2000. Effect of prescribed burning on amphibiansin the Francis Marion National Forest, SC. Abstract. TheEcological Society of America 85th Annual Meeting. Snowbird,Utah. 428 p.

Shaw C.G.; Kile, G.A. 1991. Armillaria root disease. AgricultureHandbook No. 691. U.S.D.A. Forest Service. Washington, D.C.233 p.

Westin, S. 1992. Wildfire in Missouri. Missouri Dept. ofConservation. Jefferson City, Missouri. 161 p.